The diagram illustrates the life cycle of a species of large fish called salmon.
The life cycle of a salmon starts with salmon eggs hatching in the upper river where the flow is calm and ends with adult salmon in the open sea. During the process, baby salmons get from the upper river to the lower river, where they turn into young salmon and then travel to the open sea where they mature.
At first, parent salmons choose to lay their eggs in the upper river, where the flow is slow and the eggs can be placed on tiny stones between reeds. After around 4 months, the eggs hatch, and baby salmons, which are 3 to 8 centimeters long, move to the lower river with strong flow. It takes them about 4 years here to turn into young salmons or smolts.
After that, smolts swim to the open sea, where they spend approximately 5 years growing up. An adult salmon is about 70 to 76 centimeters long, almost 5 times longer compared to their previous form. As they mature, salmons lay eggs in the upper river, where the life cycle commences.